The present invention relates to a plasma processing apparatus by low temperature plasma and more particularly to an oxidizer in which the activated gas is sent onto a samples and thereby photo resist, etc. formed on the sample surfaces is removed.
A plasma processing apparatus of the prior art, for example, as described in the bulletin of the Japanese Laid-Opened Patent No. 52-11175, proposes a method where an activating chamber made of quartz is provided to a part of a microwave cavity resonator, the oxygen gas is supplied as the raw material gas to this activating chamber and the interior is then evacuated to the predetermined degree of vacuum, the plasma is generated within the activating chamber by supplying the microwave power and the resist is oxidized by supplying the activated oxygen which is also excited by such plasma to the reactor chamber.
In the case of this method, distance between the activating chamber and reactor chamber is comparatively long. Therefore, the plasma is eliminated before it is supplied to the reactor chamber and the resist is oxidized only by the activated oxygen. Therefore, damage is not generated on the samples by plasma but the activated oxygen is also eliminated during transfer and a ratio of activated oxygen within the reactor chamber is remarkably reduced in comparison with that in the activating chamber. Concerning this point, reduction in lowering of concentration during transfer has been considered by selecting a kind of substance to be activated and a substance which collides therewith but it has been unavoidable that concentration of activated oxygen is lowered during transfer.
An apparatus of the prior art which has solved above problem is disclosed in the Japanese Laid-Opened Patent No. 56-96841. In this prior art, supply of activated oxygen is suspended in order to prevent reduction in concentration due to the supply, plasma is generated within the reactor chamber using microwave and processing speed is increased by oxidizing the resist at the activated oxygen generating region. However, the method described above does not consider damages on samples by plasma.
The prior art for solving this problem, a technique is disclosed in the Japanese Laid-Opened Patent No. 57-76844. This prior art discloses that a metal plate which screens the microwave is provided at the upper part of samples wihtin the reactor chamber in order to screen the microwave and plasma at the upper part of samples, and thereby prevents damage of samples by plasma. However, in this apparatus, since the activating chamber and the reactor chamber are located in the same chamber, the charged particles in the plasma collide with said metal plate for plasma screening and thereby the surface of metal plate is subjected to the sputtering phenomenon, material particles of metal plate are emitted to the interior of reactor chamber and these particles adhere to the samples, resulting in contamination.